arm/newlib: Add pseudomodule to enable floating point printf support

Makefile.pseudomodules

@@ -23,6 +23,7 @@ PSEUDOMODULES += schedstatistics
 PSEUDOMODULES += netif
 PSEUDOMODULES += saul_default
 PSEUDOMODULES += saul_gpio
+PSEUDOMODULES += printf_float
 
 # include variants of the AT86RF2xx drivers as pseudo modules
 PSEUDOMODULES += at86rf23%

cpu/Makefile.include.cortexm_common

@@ -95,6 +95,7 @@ include $(RIOTCPU)/cortexm_common/Makefile.include
 
 # use the nano-specs of Newlib when available
 USEMODULE += newlib_nano
+export USE_NANO_SPECS = 1
 
 # Avoid overriding the default rule:
 all:

sys/Makefile.include

@@ -63,4 +63,10 @@ ifneq (,$(filter arduino,$(USEMODULE)))
     include $(RIOTBASE)/sys/arduino/Makefile.include
 endif
 
+ifneq (,$(filter printf_float,$(USEMODULE)))
+    ifeq (1,$(USE_NANO_SPECS))
+        export LINKFLAGS += -u _printf_float
+    endif
+endif
+
 INCLUDES += -I$(RIOTBASE)/sys/libc/include

tests/printf_float/Makefile

@@ -0,0 +1,6 @@
+APPLICATION = test_printf_float
+include ../Makefile.tests_common
+
+USEMODULE += printf_float
+
+include $(RIOTBASE)/Makefile.include

tests/printf_float/main.c

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2016 Alexandre Abadie <[email protected]>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @{
+ *
+ * @file
+ * @brief       print floating point values test application
+ *
+ * This test is supposed to check that floating point values can be
+ * displayed with printf function.
+ *
+ * @author      Alexandre Abadie <[email protected]>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <inttypes.h>
+
+static const char * expected_result = "2016.0";
+static const double floating_point_value = 2016.0317;
+
+int main(void)
+{
+    const uint8_t str_len = strlen(expected_result);
+    char result[str_len];
+    snprintf(result, str_len + 1,
+             "%.f", floating_point_value);
+
+    printf("Value displayed: %s\n", result);
+
+    if (strcmp(result, expected_result) == 0) {
+        printf("[OK]\n");
+    }
+    else {
+        printf("[FAILED] Values are not equal:\n"
+               "actual: %s\n"
+               "expected: %s\n", result, expected_result);
+        return 1;
+    }
+
+    return 0;
+}